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Lee A, CingÖz O, Sabo Y, Goff SP. Characterization of interaction between Trim28 and YY1 in silencing proviral DNA of Moloney murine leukemia virus. Virology 2018; 516:165-175. [PMID: 29407374 DOI: 10.1016/j.virol.2018.01.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 01/10/2018] [Accepted: 01/12/2018] [Indexed: 10/18/2022]
Abstract
Moloney Murine Leukemia Virus (M-MLV) proviral DNA is transcriptionally silenced in embryonic cells by a large repressor complex tethered to the provirus by two sequence-specific DNA binding proteins, ZFP809 and YY1. A central component of the complex is Trim28, a scaffold protein that regulates many target genes involved in cell cycle progression, DNA damage responses, and viral gene expression. The silencing activity of Trim28, and its interactions with corepressors are often regulated by post-translational modifications such as sumoylation and phosphorylation. We defined the interaction domains of Trim28 and YY1, and investigated the role of sumoylation and phosphorylation of Trim28 in mediating M-MLV silencing. The RBCC domain of Trim28 was sufficient for interaction with YY1, and acidic region 1 and zinc fingers of YY1 were necessary and sufficient for its interaction with Trim28. Additionally, we found that residue K779 was critical for Trim28-mediated silencing of M-MLV in embryonic cells.
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Affiliation(s)
- Andreia Lee
- Department of Biological Sciences, United States
| | - Oya CingÖz
- Department of Biochemistry and Molecular Biophysics and Department of Microbiology and Immunology, Howard Hughes Medical Institute, Columbia University Medical Center, Columbia University, New York, NY 10032, United States
| | - Yosef Sabo
- Department of Biochemistry and Molecular Biophysics and Department of Microbiology and Immunology, Howard Hughes Medical Institute, Columbia University Medical Center, Columbia University, New York, NY 10032, United States
| | - Stephen P Goff
- Department of Biochemistry and Molecular Biophysics and Department of Microbiology and Immunology, Howard Hughes Medical Institute, Columbia University Medical Center, Columbia University, New York, NY 10032, United States.
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2
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Transcriptional Silencing of Moloney Murine Leukemia Virus in Human Embryonic Carcinoma Cells. J Virol 2016; 91:JVI.02075-16. [PMID: 27795446 DOI: 10.1128/jvi.02075-16] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 10/21/2016] [Indexed: 11/20/2022] Open
Abstract
Embryonic carcinoma (EC) cells are malignant counterparts of embryonic stem (ES) cells and serve as useful models for investigating cellular differentiation and human embryogenesis. Though the susceptibility of murine EC cells to retroviral infection has been extensively analyzed, few studies of retrovirus infection of human EC cells have been performed. We tested the susceptibility of human EC cells to transduction by retroviral vectors derived from three different retroviral genera. We show that human EC cells efficiently express reporter genes delivered by vectors based on human immunodeficiency virus type 1 (HIV-1) and Mason-Pfizer monkey virus (M-PMV) but not Moloney murine leukemia virus (MLV). In human EC cells, MLV integration occurs normally, but no viral gene expression is observed. The block to MLV expression of MLV genomes is relieved upon cellular differentiation. The lack of gene expression is correlated with transcriptional silencing of the MLV promoter through the deposition of repressive histone marks as well as DNA methylation. Moreover, depletion of SETDB1, a histone methyltransferase, resulted in a loss of transcriptional silencing and upregulation of MLV gene expression. Finally, we provide evidence showing that the lack of MLV gene expression may be attributed in part to the lack of MLV enhancer function in human EC cells. IMPORTANCE Human embryonic carcinoma (EC) cells are shown to restrict the expression of murine leukemia virus genomes but not retroviral genomes of the lentiviral or betaretroviral families. The block occurs at the level of transcription and is accompanied by the deposition of repressive histone marks and methylation of the integrated proviral DNA. The host machinery required for silencing in human EC cells is distinct from that in murine EC cell lines: the histone methyltransferase SETDB1 is required, but the widely utilized corepressor TRIM28/Kap1 is not. A transcriptional enhancer element from the Mason-Pfizer monkey virus can override the silencing and promote transcription of chimeric proviral DNAs. The findings reveal novel features of human EC gene regulation not present in their murine counterparts.
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Ichida Y, Utsunomiya Y, Tomikawa J, Nakabayashi K, Sato T, Onodera M. Long time-course monitoring of ZFP809-mediated gene silencing in transgene expression driven by promoters containing MLV-derived PBS. Biosci Biotechnol Biochem 2015; 80:114-20. [PMID: 26252886 DOI: 10.1080/09168451.2015.1072461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Expression of Moloney murine leukemia virus (MoMLV)-typed retroviral vectors is strictly suppressed in immature cells such as embryonic stem cells. The phenomenon known as gene silencing is primed by the sequence-specific binding of the zinc finger protein 809 (ZFP809) to the primer-binding site of the vectors. However, it has yet to be determined whether the ZFP809-mediated gene silencing is maintained over a long period. In this study, we established an experimental system that can monitor gene silencing during a long-term cell culture using flow cytometry technology combined with fluorescent reporters for the expression of ZFP809 and the transgene expression driven by the promoters of interest. Time-course analysis using our system revealed that ZFP809 maintains gene silencing effect even at a longtime period. Furthermore, our system was useful for the monitoring of ZFP809-mediated gene silencing regardless of the types of vectors and cell lines.
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Affiliation(s)
- Yu Ichida
- a Department of Human Genetics , National Research Institute for Child Health and Development , Tokyo , Japan
| | - Yuko Utsunomiya
- a Department of Human Genetics , National Research Institute for Child Health and Development , Tokyo , Japan
| | - Junko Tomikawa
- b Department of Maternal-Fetal Biology , National Research Institute for Child Health and Development , Tokyo , Japan
| | - Kazuhiko Nakabayashi
- b Department of Maternal-Fetal Biology , National Research Institute for Child Health and Development , Tokyo , Japan
| | - Toshinori Sato
- c Department of Biosciences and Informatics , Keio University , Yokohama , Japan
| | - Masafumi Onodera
- a Department of Human Genetics , National Research Institute for Child Health and Development , Tokyo , Japan
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Choi KH, Park JK, Kim HS, Uh KJ, Son DC, Lee CK. Epigenetic changes of lentiviral transgenes in porcine stem cells derived from embryonic origin. PLoS One 2013; 8:e72184. [PMID: 23977247 PMCID: PMC3747048 DOI: 10.1371/journal.pone.0072184] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 07/05/2013] [Indexed: 01/07/2023] Open
Abstract
Because of the physiological and immunological similarities that exist between pigs and humans, porcine pluripotent cell lines have been identified as important candidates for preliminary studies on human disease as well as a source for generating transgenic animals. Therefore, the establishment and characterization of porcine embryonic stem cells (pESCs), along with the generation of stable transgenic cell lines, is essential. In this study, we attempted to efficiently introduce transgenes into Epiblast stem cell (EpiSC)-like pESCs. Consequently, a pluripotent cell line could be derived from a porcine-hatched blastocyst. Enhanced green fluorescent protein (EGFP) was successfully introduced into the cells via lentiviral vectors under various multiplicities of infection, with pluripotency and differentiation potential unaffected after transfection. However, EGFP expression gradually declined during extended culture. This silencing effect was recovered by in vitro differentiation and treatment with 5-azadeoxycytidine. This phenomenon was related to DNA methylation as determined by bisulfite sequencing. In conclusion, we were able to successfully derive EpiSC-like pESCs and introduce transgenes into these cells using lentiviral vectors. This cell line could potentially be used as a donor cell source for transgenic pigs and may be a useful tool for studies involving EpiSC-like pESCs as well as aid in the understanding of the epigenetic regulation of transgenes.
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Affiliation(s)
- Kwang-Hwan Choi
- Department of Agricultural Biotechnology, Animal Biotechnology Major, and Research Institute for Agriculture and Life Science, Seoul National University, Seoul, Korea
| | - Jin-Kyu Park
- Department of Agricultural Biotechnology, Animal Biotechnology Major, and Research Institute for Agriculture and Life Science, Seoul National University, Seoul, Korea
| | - Hye-Sun Kim
- Department of Agricultural Biotechnology, Animal Biotechnology Major, and Research Institute for Agriculture and Life Science, Seoul National University, Seoul, Korea
| | - Kyung-Jun Uh
- Department of Agricultural Biotechnology, Animal Biotechnology Major, and Research Institute for Agriculture and Life Science, Seoul National University, Seoul, Korea
| | - Dong-Chan Son
- Department of Agricultural Biotechnology, Animal Biotechnology Major, and Research Institute for Agriculture and Life Science, Seoul National University, Seoul, Korea
| | - Chang-Kyu Lee
- Department of Agricultural Biotechnology, Animal Biotechnology Major, and Research Institute for Agriculture and Life Science, Seoul National University, Seoul, Korea
- * E-mail:
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5
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Fletcher AJ, Towers GJ. Inhibition of retroviral replication by members of the TRIM protein family. Curr Top Microbiol Immunol 2013; 371:29-66. [PMID: 23686231 DOI: 10.1007/978-3-642-37765-5_2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The TRIM protein family is emerging as a central component of mammalian antiviral innate immunity. Beginning with the identification of TRIM5α as a mammalian post-entry restriction factor against retroviruses, to the repeated observation that many TRIMs ubiquitinate and regulate signaling pathways, the past decade has witnessed an intense research effort to understand how TRIM proteins influence immunity. The list of viral families targeted directly or indirectly by TRIM proteins has grown to include adenoviruses, hepadnaviruses, picornaviruses, flaviviruses, orthomyxoviruses, paramyxoviruses, herpesviruses, rhabdoviruses and arenaviruses. We have come to appreciate how, through intense bouts of positive selection, some TRIM genes have been honed into species-specific restriction factors. Similarly, in the case of TRIMCyp, we are beginning to understand how viruses too have mutated to evade restriction, suggesting that TRIM and viruses have coevolved for millions of years of primate evolution. Recently, TRIM5α returned to the limelight when it was shown to trigger the expression of antiviral genes upon recognition of an incoming virus, a paradigm shift that demonstrated that restriction factors make excellent pathogen sensors. However, it remains unclear how many of ~100 human TRIM genes are antiviral, despite the expression of many of these genes being upregulated by interferon and upon viral infection. TRIM proteins do not conform to one type of antiviral mechanism, reflecting the diversity of viruses they target. Moreover, the cofactors of restriction remain largely enigmatic. The control of retroviral replication remains an important medical subject and provides a useful backdrop for reviewing how TRIM proteins act to repress viral replication.
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Affiliation(s)
- Adam J Fletcher
- MRC Centre for Medical Molecular Virology, University College, London, UK.
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6
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Rowe HM, Trono D. Dynamic control of endogenous retroviruses during development. Virology 2011; 411:273-87. [PMID: 21251689 DOI: 10.1016/j.virol.2010.12.007] [Citation(s) in RCA: 200] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Accepted: 12/06/2010] [Indexed: 02/07/2023]
Abstract
Close to half of the human genome encompasses mobile genetic elements, most of which are retrotransposons. These genetic invaders are formidable evolutionary forces that have shaped the architecture of the genomes of higher organisms, with some conserving the ability to induce new integrants within their hosts' genome. Expectedly, the control of endogenous retroviruses is tight and multi-pronged. It is most crucially established in the germ line and during the first steps of embryogenesis, primarily through transcriptional mechanisms that have likely evolved under their very pressure, but are now engaged in controlling gene expression at large, notably during early development.
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Affiliation(s)
- Helen M Rowe
- National Program, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
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7
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Multiple Epigenetic Modifiers Induce Aggressive Viral Extinction in Extraembryonic Endoderm Stem Cells. Cell Stem Cell 2010; 6:457-67. [DOI: 10.1016/j.stem.2010.03.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Revised: 01/30/2010] [Accepted: 03/05/2010] [Indexed: 11/20/2022]
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Abstract
Retroviruses are highly successful intracellular parasites, and as such they are found in nearly all branches of life. Some are relatively benign, but many are highly pathogenic and can cause either acute or chronic diseases. Therefore, there is tremendous selective pressure on the host to prevent retroviral replication, and for this reason cells have evolved a variety of restriction factors that act to inhibit or block the viruses. This review is a survey of the best-characterized restriction factors capable of inhibiting retroviral replication and aims to highlight the diversity of strategies used for this task.
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Affiliation(s)
- Daniel Wolf
- HHMI, Department of Biochemistry, Columbia University, New York, NY 10032, USA
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9
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TRIM28 mediates primer binding site-targeted silencing of murine leukemia virus in embryonic cells. Cell 2008; 131:46-57. [PMID: 17923087 DOI: 10.1016/j.cell.2007.07.026] [Citation(s) in RCA: 273] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2007] [Revised: 06/07/2007] [Accepted: 07/16/2007] [Indexed: 12/22/2022]
Abstract
Moloney murine leukemia virus (M-MLV) replication is restricted in embryonic carcinoma (EC) and embryonic stem (ES) cells, likely to protect the germ line from insertional mutagenesis. Proviral DNAs are potently silenced at the level of transcription in these cells. This silencing is largely due to an unidentified trans-acting factor that is thought to bind to the primer binding site (PBS) of M-MLV and repress transcription from the viral promoter. We have partially purified a large PBS-mediated silencing complex and identified TRIM28 (Kap-1), a known transcriptional silencer, as an integral component of the complex. We show that RNAi-mediated knockdown of TRIM28 in EC and ES cells relieves the restriction and that TRIM28 is bound to the PBS in vivo when restriction takes place. The identification of TRIM28 as a retroviral silencer adds to the growing body of evidence that many TRIM family proteins are involved in retroviral restriction.
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Hamanaka S, Nabekura T, Otsu M, Yoshida H, Nagata M, Usui J, Takahashi S, Nagasawa T, Nakauchi H, Onodera M. Stable Transgene Expression in Mice Generated from Retrovirally Transduced Embryonic Stem Cells. Mol Ther 2007; 15:560-5. [PMID: 17180117 DOI: 10.1038/sj.mt.6300063] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Silencing of transduced genes hampers production of transgenic mice using retroviral vectors. We show stable expression of the enhanced green fluorescent protein (EGFP) gene in chimeric mice generated from retrovirally transduced embryonic stem cells. The vector was a murine stem cell virus-typed retroviral vector (GCDsap) in which the long terminal repeat and primer-binding site were derived from a PCC4 cell-passaged myeloproliferative sarcoma virus and the endogenous retrovirus dl587rev, respectively. To increase the viral titer, the vector was packaged with vesicular stomatitis virus G protein, which allowed concentration of the virus into pellets followed by resuspension in serum-free medium. In chimeric mice, EGFP was detected in various tissues including hematopoietic cells, neurons, cardiac muscle, and intestine. Furthermore, high expression was maintained in the progeny of these mice, suggesting successful germline transmission of active proviruses. Although the proportion of EGFP-expressing cells and the mean intensity of EGFP expression varied among tissues and mice, 100% of peripheral blood leukocytes expressed EGFP in mice carrying a single provirus copy, as well as in their progeny. Therefore, the gene transfer system described here provides a useful tool not only to generate transgenic animals but also to manipulate human embryonic stem cells..
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Affiliation(s)
- Sanae Hamanaka
- Major of Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan
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11
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Wang J, Li ML, Hua D, Chen Q. Exonuclease-mediated ELISA-like assay for detecting DNA-binding activity of transcription factors: measurement of activated NF-kappaB. Biotechniques 2006; 41:79-88, 90. [PMID: 16869518 DOI: 10.2144/000112218] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
This paper describes an exonuclease-mediated enzyme-linked immunosorbent assay (ELISA)-like assay (EMEA) for detecting the DNA binding activity of nuclear factor kappaB (NF-kappaB). For EMEA, a special double-stranded DNA (dsDNA)-coupled plate was first prepared by immobilizing a DNA probe on an N-oxysuccinimide ester-coated plate. The immobilized DNA probe, which was internally labeled with digoxigenin (DIG)-dT contained a NF-kappaB binding consensus sequence for capturing activated NF- kappaB in analyzed samples. For measurement, the plate was first incubated with a protein sample and then treated with exonuclease III to eliminate the probes not bound by NF-kappaB. Finally, the probes protected by NF-kappaB were colorimetrically detected by an alkaline phosphatase (AP)-conjugated anti-DIG antibody. The major advantage of EMEA is that it detects NF-kappaB without the need for NF-kappaB antibodies. EMEA may provide a general approach for assays of DNA sequence-specific transcription factors for which specific antibodies are unavailable, expensive, or of insufficient quality.
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Affiliation(s)
- Jinke Wang
- State Key laboratory of Bioelectronics, Southeast University, Nanjing, China.
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12
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Abstract
Transgenic animal technology is one of the most fascinating technologies developed in the last two decades. It allows us to address questions in life sciences that no other methods have achieved. The impact on biomedical and biological research, as well as commercial interests are overwhelming. The questions accompanying this fast growing technology and its diversified applications attract the attention from a variety of entities. Still, one of the most fundamental problems remaining is the search for an efficient and reliable gene delivery system for creating transgenic animals. The traditional method of pronuclear microinjection has displayed great variability in success among species. While an acceptable efficiency in the production of transgenic mice has been attained, the relative low efficiency (<1%) in creating transgenic livestock has become one of the barriers for its application. In the past decades, improvements in producing transgenic livestock have made a slow progression, however, the recent advancement in cloning technology and the ability to create transgenic livestock in a highly efficient manner, have opened the gate to a new era in transgenic technology. Discoveries of new gene delivery systems have created an enthusiastic atmosphere that has made this technology so unique. This review focuses on gene delivery strategies as well as various approaches that may assist the advancement of transgenic efficiency in large animals.
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Affiliation(s)
- A W Chan
- Oregon Regional Primate Research Center, Oregon Health Sciences University, Beaverton, Oregon 97006, USA.
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13
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Amit M, Winkler ME, Menke S, Brüning E, Büscher K, Denner J, Haverich A, Itskovitz-Eldor J, Martin U. No evidence for infection of human embryonic stem cells by feeder cell-derived murine leukemia viruses. Stem Cells 2005; 23:761-71. [PMID: 15917472 DOI: 10.1634/stemcells.2004-0046] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Until recently, culture and expansion of nondifferentiated human embryonic stem cells (hESCs) depended on coculture with murine embryonic fibroblasts. Because mice are known to harbor a variety of pathogens, such culture conditions implicate the risk of xenozoonoses. Among these pathogens, endogenous retroviruses, including murine leukemia viruses (MuLVs), are of special importance. It is well known that some strains cause pathogenic (e.g., leukemic) effects and that xenotropic, polytropic, and amphotropic MuLVs are able to infect human cells. In view of potential clinical applications of hESC lines, it is therefore imperative to investigate potential infection of hESCs by mouse feeder cell-derived viruses. As a first step towards a comprehensive infection risk assessment, we have analyzed embryonic fibroblasts derived from different mouse strains for expression and release of xenotropic, polytropic, and amphotropic MuLVs. Moreover, several hESC lines have been investigated for expression of specific receptors for xenotropic/polytropic MuLVs, as well as for MuLV infection and expression. Evidence for expression of humantropic MuLVs was found in cultures of mouse embryonic fibroblasts (MEFs). Moreover, expression of specific receptors for xenotropic/ polytropic MuLV on human HEK293 and hESC lines and infection after coculture with an MuLV-producing mink cell line could be demonstrated. In contrast, no evidence of MuLV transmission from MEFs to human HEK293 cells or to the hESC lines I-3, I-6, I-8, and H-9 has been obtained. Our results suggest that recently established hESC lines are free of MuLV infections despite long-term close contact with MEFs.
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Affiliation(s)
- Michal Amit
- Department of Obstetrics and Gynecology, Rambam Medical Center, Faculty of Medicine, The Technion, Haifa, Israel
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14
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Nagata M, Takahashi M, Muramatsu SI, Ueda Y, Hanazono Y, Takeuchi K, Okada K, Suzuki Y, Kondo Y, Suemori M, Ikeda U, Nakano I, Kobayashi E, Hasegawa M, Ozawa K, Nakatsuji N, Shimada K. Efficient gene transfer of a simian immuno-deficiency viral vector into cardiomyocytes derived from primate embryonic stem cells. J Gene Med 2004; 5:921-8. [PMID: 14601129 DOI: 10.1002/jgm.431] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND Embryonic stem (ES) cells continually proliferate and can generate large numbers of differentiated cells. Genetic manipulation of transplantable cells derived from primate ES cells offers considerable potential for development research and regenerative cell therapy. However, protocols for efficient gene transfer into primate ES-cell-derived cells have not yet been established. METHODS Spontaneously contracting areas were derived from cynomolgus monkey ES cells. Features of cardiomyocytes in the area were analyzed according to gene expression (RT-PCR), morphology (immunostaining and electron microscopy), and function (intracellular calcium transience). Beating cells were transduced using a simian immunodeficiency virus (SIV) vector expressing enhanced green fluorescence protein (EGFP), then transplanted into ischemic rat myocardium. RESULTS Beating cells derived from monkey ES cells displayed gene expression, ultrastructural and functional properties of early-stage cardiomyocytes. Highly efficient (97% cardiac phenotype) and stable transduction of these ES-cell-derived cardiomyocytes was achieved using SIV vector without altering contractile function. In addition, transduced cardiomyocytes survived in the myocardium of a rat myocardial infarction model. CONCLUSIONS A lentiviral vector system based on SIV represents a useful vehicle for genetic modification of cardiomyocytes derived from primate ES cells, and can extend the application of primate ES cells to gene therapy.
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Affiliation(s)
- Mihoko Nagata
- Department of Medicine, Jichi Medical School, Tochigi 329-0498, Japan
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15
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Iba H, Mizutani T, Ito T. SWI/SNF chromatin remodelling complex and retroviral gene silencing. Rev Med Virol 2003; 13:99-110. [PMID: 12627393 DOI: 10.1002/rmv.378] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Because of the unique infectious cycle of retroviruses which involves the integration of the retroviral genome into the host chromosome, many cellular chromosomal proteins are used by the virus to maintain its gene expression. At the same time, cellular mechanisms for the surveillance and exclusion of non-self expression by such intragenomic parasites operate as an important host defence system in the cellular nuclei. Retroviruses have strategies for escaping from host defence systems, such as by maintaining or reactivating viral expression in specific host cell types. Understanding such epigenetical regulation would be essential for progress in retroviral virology. In this review, we emphasise the importance of the chromatin remodelling factor SWI/SNF complex as one of the key players in epigenetic regulation of host and viral gene expression. An understanding of these mechanisms will surely lead to new ideas on the pathogenicity of this virus, on the latent infection observed in many other viruses, and further forward the design of unique retroviral vectors for long-term transgene expression, providing strong tools for human gene therapy and regenerative medicine.
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Affiliation(s)
- Hideo Iba
- Division of Host-Parasite Interaction, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
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16
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Prasad Alur RK, Foley B, Parente MK, Tobin DK, Heuer GG, Avadhani AN, Pongubala J, Wolfe JH. Modification of multiple transcriptional regulatory elements in a Moloney murine leukemia virus gene transfer vector circumvents silencing in fibroblast grafts and increases levels of expression of the transferred enzyme. Gene Ther 2002; 9:1146-54. [PMID: 12170378 DOI: 10.1038/sj.gt.3301777] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2002] [Accepted: 03/07/2002] [Indexed: 11/09/2022]
Abstract
Down-regulation of retroviral vector expression occurs in a number of cell types after transplantation. Although a number of vector elements have been shown to affect expression in specific experimental situations, the results can vary depending on the specific cDNA being expressed, the individual retroviral elements included in vectors, the promoter, or the inclusion of selectable markers. In previous experiments with the lysosomal enzyme beta-glucuronidase, silencing has occurred in more than 95% of transduced cells regardless of the position of the expression unit within the vector, whether a eukaryotic or viral promoter was used, whether a bacterial selectable marker gene was present or not, the target cell type, or the species of the host. It has been a consistent finding that a small number of continuously expressing cells persist for long periods after transplantation. In this study we found that deletion of all the transcriptional regulatory elements from the vector LTR, inclusion of a permissive primer binding site sequence, and use of a eukaryotic housekeeping promoter could greatly increase the number of expressing cells in fibroblast grafts in subcutaneous neo-organs and in the brain. Furthermore, the level of enzyme expression was increased five-fold on a per positive cell basis, indicating that the deleted regulatory elements were exerting a negative effect on expression in the few cells that were positive before modification of the vector. This resulted in more than a 50-fold increase in total activity compared with the previous highest expressing vector.
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Affiliation(s)
- R K Prasad Alur
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, PA 19104, USA
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17
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Swindle CS, Klug CA. Mechanisms that regulate silencing of gene expression from retroviral vectors. JOURNAL OF HEMATOTHERAPY & STEM CELL RESEARCH 2002; 11:449-56. [PMID: 12183830 DOI: 10.1089/15258160260090915] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The propensity of retroviruses toward transcriptional silencing limits their value as gene therapy vectors. Silencing has been shown to be particularly robust when stem cells are used for transduction, posing a significant problem for gene therapy of hematologic diseases. Stability of proviral expression with newer generation vectors is significantly improved over that obtainable with original vectors based on Moloney murine leukemia virus (MoMLV). However, strategies to increase resistance further to retroviral silencing are needed, because newer generation vectors have been shown to remain prone to a significant degree of silencing that could limit their efficacy as gene therapy vectors. Proviral silencing has been attributed to known mechanisms of cellular gene repression, such as DNA methylation and histone modification, as well as uncharacterized mechanisms that act independently of DNA methylation. A further understanding of transcriptional silencing that occurs in stem cells and during hematopoietic development is needed for design of effective vectors for gene therapy of hematologic diseases.
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Affiliation(s)
- C Scott Swindle
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294-3300, USA
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18
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Ketteler R, Glaser S, Sandra O, Martens UM, Klingmüller U. Enhanced transgene expression in primitive hematopoietic progenitor cells and embryonic stem cells efficiently transduced by optimized retroviral hybrid vectors. Gene Ther 2002; 9:477-87. [PMID: 11948372 DOI: 10.1038/sj.gt.3301653] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2001] [Accepted: 12/11/2001] [Indexed: 11/09/2022]
Abstract
Oncoretroviral vectors have been successfully used in gene therapy trials, yet low transduction rates and loss of transgene expression are still major obstacles for their application. To overcome these problems we modified the widely used Moloney murine leukemia virus-derived retroviral vector pMX by replacing the 3'LTR with the spleen focus-forming virus LTR and inserting the woodchuck hepatitis B virus post-translational regulatory element. To compare requirements crucial for efficient transgene expression, we generated the hybrid retroviral vectors pMOWS and pOWS that harbor the complete murine embryonic stem cell virus (MESV)-leader sequence or a shortened MESV-leader not comprising primer binding site (PBS) and splice donor (SD). Applying these retroviral vectors significantly augmented transgene expression in hematopoietic cell lines and progenitor cells. For transduction of murine embryonic stem (ES) cells the retroviral vector pMOWS that harbors the MESV-PBS and -SD was superior resulting in 65% green fluorescent protein (GFP) expressing ES cells. Surprisingly, in murine and human primitive hematopoietic progenitor cells (HPC), the highest efficiency of up to 66% GFP expressing cells was achieved with pOWS, a retroviral vector that retains the negative regulatory element coinciding with the MoMuLV-PBS. In summary our hybrid retroviral vectors facilitate significantly improved transgene expression in multipotent cells and thus possess great potential for reconstituting genes in primary cells of disease models, as well as for gene therapy.
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Affiliation(s)
- R Ketteler
- Hans-Spemann Laboratories, Max-Planck Institute of Immunobiology, Freiburg, Germany
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19
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García-Martín C, Chuah MKL, Van Damme A, Robinson KE, Vanzieleghem B, Saint-Remy JM, Gallardo D, Ofosu FA, Vandendriessche T, Hortelano G. Therapeutic levels of human factor VIII in mice implanted with encapsulated cells: potential for gene therapy of haemophilia A. J Gene Med 2002; 4:215-23. [PMID: 11933222 DOI: 10.1002/jgm.248] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND A gene therapy delivery system based on microcapsules enclosing recombinant cells engineered to secrete a therapeutic protein has been evaluated. The microcapsules are implanted intraperitoneally. In order to prevent cell immune rejection, cells are enclosed in non-antigenic biocompatible alginate microcapsules prior to their implantation into mice. It has been shown that encapsulated myoblasts can deliver therapeutic levels of Factor IX (FIX) in mice. The delivery of human Factor VIII (hFVIII) in mice using microcapsules was evaluated in this study. METHODS Mouse C2C12 myoblasts and canine MDCK epithelial kidney cells were transduced with MFG-FVIII (B-domain deleted) vector. Selected recombinant clones were enclosed in alginate microcapsules. Encapsulated recombinant clones were subsequently implanted intraperitoneally into C57BL/6 and immunodeficient SCID mice. RESULTS Plasma of mice receiving C2C12 and encapsulated MDCK cells had transient therapeutic levels of FVIII in immunocompetent C57BL/6 mice (up to 20% and 7% of physiological levels, respectively). In addition, FVIII delivery in SCID mice was also transient, suggesting that a non-immune mechanism must have contributed to the decline of hFVIII in plasma. Quantitative RT-PCR analysis confirmed directly that the decline of hFVIII is due to a reduction in steady-state hFVIII mRNA, consistent with transcriptional repression. Furthermore, encapsulated cells retrieved from implanted mice were viable, but secreted FVIII ex vivo at three-fold lower levels than the pre-implantation levels. In addition, antibodies to hFVIII were detected in immunocompetent C57BL/6 mice. CONCLUSIONS Implantable microcapsules can deliver therapeutic levels of FVIII in mice, suggesting the potential of this gene therapy approach for haemophilia A. The findings suggest vector down-regulation in vivo.
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Affiliation(s)
- Carmen García-Martín
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
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20
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Modin C, Lund AH, Schmitz A, Duch M, Pedersen FS. Alleviation of murine leukemia virus repression in embryonic carcinoma cells by genetically engineered primer binding sites and artificial tRNA primers. Virology 2000; 278:368-79. [PMID: 11118360 DOI: 10.1006/viro.2000.0683] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The primer binding site (PBS) plays pivotal roles during reverse transcription of retroviruses and also is the target of a cellular host defense impeding the transcription of murine leukemia virus (MLV) harboring a proline (pro) PBS in embryonic cells. Both the PBS and the tRNA primer are copied during reverse transcription and anneal as complementary DNA sequences creating the PBS of the integrated provirus. The pro PBS of MLV can be exchanged by PBS sequences matching endogenous or engineered tRNAs to allow replication of Akv MLV-derived vectors in fibroblasts. Here we use the PBS escape mutant B2 to demonstrate the capacity of the synthetic tRNA(B2) to function in reverse transcription in competition with endogenous tRNAs in fibroblasts and embryonic carcinoma (EC) cells. We further show symmetry between PBS and the primer by the ability of the synthetic tRNA(B2) to confer escape from EC repression of a PBS-Pro vector. Of a panel of vectors with the repressed pro PBS substituted for other natural or artificial PBS sequences, all except one efficiently expressed the neo marker gene when transferred to NIH/3T3 and EC cells, hence avoiding PBS-mediated silencing in EC cells. A non-natural PBS matching an artificially designed tRNA molecule conferred no further relief from repression than that attained with the B2 escape mutant or the natural alternative PBSs. Interestingly, a vector harboring a PBS matching tRNA(Lys1.2) suffered repression similar to the wild-type PBS-Pro but was partially rescued by a single point mutation of the PBS.
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Affiliation(s)
- C Modin
- Department of Molecular and Structural Biology, University of Aarhus, Aarhus C, DK-8000, Denmark
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21
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Chuah MK, Van Damme A, Zwinnen H, Goovaerts I, Vanslembrouck V, Collen D, VandenDriessche T. Long-term persistence of human bone marrow stromal cells transduced with factor VIII-retroviral vectors and transient production of therapeutic levels of human factor VIII in nonmyeloablated immunodeficient mice. Hum Gene Ther 2000; 11:729-38. [PMID: 10757352 DOI: 10.1089/10430340050015626] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The potential of using bone marrow (BM)-derived human stromal cells for ex vivo gene therapy of hemophilia A was evaluated. BM stromal cells were transduced with an intron-based Moloney murine leukemia virus (Mo-MuLV) retroviral vector that contained the B domain-deleted human factor VIII (FVIIIdeltaB) cDNA. This FVIII-retroviral vector was pseudotyped with the gibbon ape leukemia virus envelope (GALV-env) to attain higher transduction efficiencies. Using optimized transduction methods, high in vitro FVIII expression levels of 700 to 2500 mU of FVIII/10(6) cells per 24 hr were achieved without selective enrichment of the transduced BM stromal cells. After xenografting of 1.5-3 x 106 engineered BM stromal cells into the spleen of nonobese diabetic severe combined immunodeficient (NOD-SCID) mice, human plasma FVIII levels rose to 13 +/- 4 ng/ml but declined to basal levels by 3 weeks postinjection because of promoter inactivation. About 10% of these stromal cells engrafted in the spleen and persisted for at least 4 months after transplantation in the absence of myeloablative conditioning. No human BM stromal cells could be detected in other organs. These findings indicate that retroviral vector-mediated gene therapy using engineered BM stromal cells may lead to therapeutic levels of FVIII in vivo and that long-term engraftment of human BM stromal cells was achieved in the absence of myeloablative conditioning and without neo-organs. Hence, BM stromal cells may be useful for gene therapy of hemophilia A, provided prolonged expression can be achieved by using alternative promoters.
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Affiliation(s)
- M K Chuah
- Center for Transgene Technology and Gene Therapy, Flanders Interuniversity Institute for Biotechnology, University of Leuven, Belgium
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22
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Kitamura M. Bystander macrophages silence transgene expression driven by the retroviral long terminal repeat. Biochem Biophys Res Commun 1999; 257:74-8. [PMID: 10092512 DOI: 10.1006/bbrc.1999.0414] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Moloney murine leukemia virus (MLV)-based retroviral vector has been widely used for transfer of exogenous genes to various organs and tissues. Although the long terminal repeat (LTR) of MLV allows for transgene expression in a wide range of cell type, its activity is often silenced in vivo. In reporter macrophages transduced with a MLV-based retroviral vector, activity of the LTR was transiently and reversibly suppressed following stimulation by lipopolysaccharide (LPS). When unstimulated reporter macrophages were co-cultured with LPS-stimulated, untransduced macrophages, the LTR activity was similarly depressed. Activity of the LTR in retrovirus-transduced, mesangial cells was also down-regulated when co-cultured with activated macrophages. This suppressive effect was reproduced by cross-feeding with culture media conditioned by activated macrophages. LPS-stimulated macrophages abundantly expressed cytokines including IL-1beta, tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta1 (TGF-beta1). When externally added, TNF-alpha and/or TGF-beta1, but not IL-1beta, depressed activity of the LTR in reporter macrophages and reporter mesangial cells. These results raise a possibility that expression of transgenes driven by the MLV-LTR may be silenced in vivo when the retrovirally-transduced cells are co-localized with activated macrophages.
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Affiliation(s)
- M Kitamura
- Department of Medicine, University College London Medical School, The Rayne Institute, 5 University Street, London, WC1E 6JJ, United Kingdom.
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23
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Abstract
The interaction of proteins with DNA is a central theme of molecular biology. In this article, we review some of the principal techniques currently used for the identification and characterization of DNA binding proteins, and for investigation of the molecular interactions that are responsible for the recognition of specific DNA sequences.
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Affiliation(s)
- M J Guille
- Division of Molecular and Cell Biology, School of Biological Science, University of Portsmouth, UK
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24
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Kotomura N, Ninomiya Y, Umesono K, Niwa O. Transcriptional regulation by competition between ELP isoforms and nuclear receptors. Biochem Biophys Res Commun 1997; 230:407-12. [PMID: 9016793 DOI: 10.1006/bbrc.1996.5972] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
ELP is a transcription factor belonging to the nuclear receptor superfamily. The consensus binding sequence for ELP contains a half site of the nuclear receptor recognition element. We demonstrated previously that ELP1, the repressor type isoform of ELP, competes for binding with the retinoic acid receptor and represses retinoic acid-induced transactivation. In this study, competitive repression by ELP1 was investigated for several other nuclear receptors. As in the case of the retinoic acid receptor, binding of vitamin D receptor, thyroid hormone receptor, and estrogen receptor could be competed by ELP1, resulting in repression of their ligand-dependent transactivation. Interestingly, the activator-type ELP isoforms were capable of repressing retinoic acid-induced transactivation through binding to the retinoic acid receptor binding element. These data suggest that competition for target DNA binding is a general mechanism of transcriptional repression by ELP isoforms.
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Affiliation(s)
- N Kotomura
- Department of Molecular Pathology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Kasumi, Mimami-ku, Japan
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25
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Lund A, Duch M, Pedersen F. Transcriptional Silencing of Retroviral Vectors. J Biomed Sci 1996; 3:365-378. [PMID: 11725119 DOI: 10.1007/bf02258042] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Although retroviral vector systems have been found to efficiently transduce a variety of cell types in vitro, the use of vectors based on murine leukemia virus in preclinical models of somatic gene therapy has led to the identification of transcriptional silencing in vivo as an important problem. Extinction of long-term vector expression has been observed after implantation of transduced hematopoietic cells as well as fibroblasts, myoblasts and hepatocytes. Here we review the influence of vector structure, integration site and cell type on transcriptional silencing. While down-regulation of proviral transcription is known from a number of cellular and animal models, major insight has been gained from studies in the germ line and embryonal cells of the mouse. Key elements for the transfer and expression of retroviral vectors, such as the viral transcriptional enhancer and the binding site for the tRNA primer for reverse transcription may have a major influence on transcriptional silencing. Alterations of these elements of the vector backbone as well as the use of internal promoter elements from housekeeping genes may contribute to reduce transcriptional silencing. The use of cell culture and animal models in the testing and improvement of vector design is discussed. Copyright 1996 S. Karger AG, Basel
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Affiliation(s)
- A.H. Lund
- Department of Molecular and Structural Biology, University of Aarhus, Denmark
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26
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Vernet M, Cebrian J. cis-acting elements that mediate the negative regulation of Moloney murine leukemia virus in mouse early embryos. J Virol 1996; 70:5630-3. [PMID: 8764077 PMCID: PMC190523 DOI: 10.1128/jvi.70.8.5630-5633.1996] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We have addressed the question of the nature of Moloney murine leukemia virus (MoMuLV) repression in mouse embryos by assaying for the transient expression of MoMuLV-derived constructs microinjected into early cleavage embryos. We show that the same cis-acting DNA sequences responsible for the block in MoMuLV expression in embryonal carcinoma cell lines operate in early embryos: (i) the MoMuLV long terminal repeat is nonfunctional, and (ii) the +147 to +163 repressor binding site, or negative regulatory element, negatively regulates the expression from an active promoter.
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Affiliation(s)
- M Vernet
- Institut Cochin de Génétique Molécularire, Laboratoire de Génétique et Pathologie Expérimentales, Unité 380 de l'Institut National de la Santé et de la Recherche Médicale, Paris, France
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27
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28
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Delouis C, Bonnerot C, Vernet M, Nicolas JF. Expression of microinjected DNA and RNA in early rabbit embryos: changes in permissiveness for expression and transcriptional selectivity. Exp Cell Res 1992; 201:284-91. [PMID: 1379192 DOI: 10.1016/0014-4827(92)90275-d] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Gene expression in rabbit early development was investigated by microinjecting LacZ DNA and LacZ RNA in 1-cell and 2-cell embryos. Expression of LacZ DNA could not be obtained before 30-36 hpf, although synthetic LacZ RNA was translated from 12 hpf at the least. The onset of expression of microinjected DNA correlated with the 8- to 16-cell stage. This suggests that before this stage, there is a general negative control of gene expression. The arrest of in vitro development at the 2- to 8-cell stages did not inhibit LacZ expression, which still occurred at 33 hpf. In addition the inhibition of the first cleavage by nocodazole resulted in LacZ expression in 1-cell embryos. Expression of microinjected DNA thus occurs at a fixed time after fertilization and is independent of cleavages and of the second and subsequent DNA replications. Therefore, the changes in permissiveness for the expression of microinjected DNA in rabbit embryos are reminiscent of those in mouse embryos. Transcriptional selectivity in rabbit embryos was compared to that in early mouse embryos. In both species, Sp1-sensitive promoters were active and the promoter of simian virus 40 did not require far upstream enhancers before late cleavage stages; genes driven by the -447, +563 region of murine leukemia virus were repressed. In rabbit, however, the H-2Kb promoter active in mouse was silent. Altogether, the results illustrate a remarkable conservation of the characteristics of the transcription in early rabbit and mouse embryos and the independence of its resumption from the pattern of cleavage.
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Affiliation(s)
- C Delouis
- Station de Physiologie Animale, INRA, Jouy-En-Josas, France
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29
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Abstract
Significant advances have been made in precisely defining the elements in the Moloney murine leukemia virus genome responsible for tissue-restricted expression. This knowledge should lead to improved expression vectors for gene transfer in mammalian cells. In the past year, retrovirus-mediated gene expression in a diverse range of cell types has been reported. These cells have been used to study gene transfer relevant to a range of inherited diseases.
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30
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Beck-Engeser G, Stocking C, Just U, Albritton L, Dexter M, Spooncer E, Ostertag W. Retroviral vectors related to the myeloproliferative sarcoma virus allow efficient expression in hematopoietic stem and precursor cell lines, but retroviral infection is reduced in more primitive cells. Hum Gene Ther 1991; 2:61-70. [PMID: 1863641 DOI: 10.1089/hum.1991.2.1-61] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Retroviral vectors are considered to be the most suited vehicles for somatic gene therapy with hematopoietic stem cells as targets. Retrovirus-mediated gene transfer into differentiation-restricted hematopoietic precursor (FDC-P1, FDC-P2) and multipotent progenitor (stem) cell lines (FDC-Pmix) is inefficient. Two cellular restrictions are involved. One is specific for stem but not precursor cells and is at the level of transcription. Due to a unique property of the transcriptional control region of the myeloproliferative sarcoma virus (MPSV), vectors derived from MPSV are not affected by this block. The second restriction occurs before proviral DNA synthesis and integration. This inhibition of effective viral infection depends on the state of differentiation, being more pronounced in multipotent clonogenic blast cells. This block to retroviral infection affects all retroviral vectors tested.
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Affiliation(s)
- G Beck-Engeser
- Heinrich-Pette-Institut für Experimentelle Virologie und Immunologie, Universität Hamburg, Federal Republic of Germany
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31
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Prince VE, Rigby PW. Derivatives of Moloney murine sarcoma virus capable of being transcribed in embryonal carcinoma stem cells have gained a functional Sp1 binding site. J Virol 1991; 65:1803-11. [PMID: 1848307 PMCID: PMC239988 DOI: 10.1128/jvi.65.4.1803-1811.1991] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The long terminal repeat (LTR) sequences of Moloney murine leukemia virus and its closely related derivative Moloney murine sarcoma virus (Mo-MSV) are incapable of directing transcription in embryonal carcinoma (EC) stem cells. The myeloproliferative sarcoma virus, a derivative of Mo-MSV, has several point mutations in the LTR and is transcribed more efficiently to allow productive infection of F9 EC cells. One of these mutations, at -166 with respect to the transcriptional start, creates a consensus binding site for the well-characterized mammalian transcription factor Sp1. We used gel retardation assays to demonstrate that F9 EC cell extracts form several complexes with the myeloproliferative sarcoma virus sequence around -166. One of these complexes involves a murine Sp1-like protein, which has immunoreactivity, DNA binding specificity, and electrophoretic mobility equivalent to those of purified human Sp1 protein. An equivalent complex forms on the corresponding Mo-MSV sequence but with a fivefold-lower affinity. Consistent with these observations, introduction of the single point mutation at -166 into the Mo-MSV LTR, creating a consensus Sp1 binding site, increases expression in F9 EC cells sixfold.
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Affiliation(s)
- V E Prince
- Laboratory of Eukaryotic Molecular Genetics, National Institute for Medical Research, The Ridgeway, London, England
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32
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Kung HJ, Boerkoel C, Carter TH. Retroviral mutagenesis of cellular oncogenes: a review with insights into the mechanisms of insertional activation. Curr Top Microbiol Immunol 1991; 171:1-25. [PMID: 1814689 DOI: 10.1007/978-3-642-76524-7_1] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- H J Kung
- Department of Molecular Biology and Microbiology, Case Western Reserve University, School of Medicine, Cleveland, OH 44106
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